[postgis-tickets] [PostGIS] #1014: GEOMETRY type is not "hashable"

[PostGIS]

#1014: GEOMETRY type is not "hashable"
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  Reporter:  vince        |      Owner:  pramsey
      Type:  enhancement  |     Status:  reopened
  Priority:  medium       |  Milestone:  PostGIS 2.2.0
 Component:  postgis      |    Version:  trunk
Resolution:               |   Keywords:  GEOMETRY hash UNION
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Changes (by pramsey):

 * status:  closed => reopened
 * resolution:  wontfix =>
 * version:  1.5.X => trunk
 * type:  defect => enhancement
 * milestone:  PostGIS 1.5.3 => PostGIS 2.2.0


Comment:

 I'm finding it hard to care about the issue mentioned in Mark's article.
 Basically, if I'm reading it right, it means that our hashing would
 provide a different value for:

 POINT(0 0) and POINT(-0 0)

 So if you tried to test equality with the hash function, you'd be told
 they aren't equal. And if you did a SELECT 'POINT(0 0)' UNION SELECT
 POINT(-0 0) you'd get back two rows instead of one.

 This seems like hardly a deathly issue, and I being too cowboy here? We're
 already consuming POINT(NaN NaN) for infrastructural purposes, and not
 allowing convenient CTE recursion (in all cases) because we might
 accidentally duplicate 0 and -0 cases? Seem like nose cutting and face
 spiting.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/1014#comment:11>
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